1. Field of the Invention
The present invention relates generally to an earphone and more particularly, to a water-repellent earphone which can drain moisture quickly to prevent the built-in speaker from damage and enhance the acoustic performance.
2. Description of the Related Art
A regular earphone includes a venthole that is usually located at the rear side of the housing. When a speaker of the earphone emits sound, a venthole and a waterproof ventilative member covering the venthole jointly regulate the inflow and outflow of a gas inside a rear chamber of the earphone, thus reducing the pressure of the gas and affecting the acoustic performance of the earphone particularly for frequency response within low-frequency range.
A conventional earphone, e.g. U.S. Pat. No. 4,646,872, referring to FIG. 2, includes a housing 2 having a receiving space for receiving a speaker unit 1. A duct 7 is formed at a rear end of the housing 2 for communication with an opening of a housing cap 9 for making a gas inside a rear cavity 8 communicable with the external environment. To prevent moisture from entering the rear cavity 8, this patent disclosed a waterproof ventilative mesh 10 for covering the opening the rear cavity 9. In addition, a series of tests are applied to the frequency response of the earphone after the earphone is soaked in or doused with water. Referring to FIGS. 6 and 7 of this patent, when the earphone is wiped dry after it is soaked or doused with water, the frequency response of the earphone within the low-frequency range lowers to a certain degree and as the time passes by, the gain of the low-frequency range gradually is restored as what it is before soaked in or doused with water.
Although it is known from the aforesaid patent that the moisture indeed affects the earphone, that patent is devoid of an applicable drainage protocol, so the earphone fails to expel the moisture quickly, after it is soaked in or doused with water, and to enhance the frequency response within the low-frequency range up to what it is before the earphone soaked in or doused with water. For this reason, this conventional earphone needs further improvement.